Safety device for preventing accidental erasing or double recording on magnetic record tape



Sept. 30, 1952 s, HELLER 2,612,565

SAFETY DEVICE FOR PREVENTING ACCIDENTAL ERASING 0R DOUBLE RECORDING ON MAGNETIC RECORD TAPE Filed May 24, 1948 2 SHEETSSHEET l O m Om m w; om 6r m I I I ..,.n........,-.,.......,,,... ."r

e E. m T. m V W HEBMfl/V 5. HELL HTTOBNEV Sept. 30, 1952 Filed May .24, 1948 H S. HELLER I 2,612,565 SAFETY DEVICE FOR PREVENTING ACCIDENTAL ERASIN OR DOUBLE RECORDING ON MAGNETIC RECORD TAPE 2 SHEETS-SHEET 2 HMPUFYSQ Hem/nu 51 #544519,

INVENTOR.

HTTOENE'V however,

embodiment thereof. accompanying drawings, in which:

Patented Sept. 30, 1952 UNITED STATES PATENT SAFETY DEVICE FOR PREVENTING ACCI- DENTAL ERASING on DOUBLE RECORD- ING N MAGNETIC RECORD TAPE Herman S. Heller, West Los Angeles, Calif.

Application May 24, 1948, Serial No. 28,834 3 Claims. (01.1'79-1002) This invention relates generally to magnetic sound recording and reproducing machines, and

while the invention is not limited thereto, my preferred and illustrative form of such a machine employs a separable record magazine carrying a record of the tape type.

It is well known that magnetic sound records are capable-of being very readily erased from therecord medium. This may be accomplished by either demagnetizing the record, magnetizing portant recording thereby obliterated. Again, it may happen that the recording circuit is mistakenly energized, causing a second recording to be superimposed over the original, thus ruining the latter.

It is accordingly a primary object of the present invention to provide a safeguarding means preventing inadvertent erasing or superimposed double recording for certain conditions of operation of the machine. 7 While the invention may be carried into effect in various ways, it is conveniently and illustratively appliedto a type of machine having record time magazines which are separable from the machine and thus readilyinterchangeable. Ac-

cording to this preferred application of the invention, a tie-commissioning switch means is employed in' the electric circuit of the erasing and translating electromagnets, and is arranged to be actuated by the operation of mounting a record magazine-on the machine. Withthis switch actuated,-the erasing and recording functions of the magnets are killed, and there is no possiblity therefore of obliterating a recording previously made on the record tape, --There'is also provided, a means whereby the de-commissioning switch means can be released, so that the record on the tape in the magazine can be erased and a new recording made according to the usual practice. r v

- The invention also provides certain related immovements in magnetic sound recording machines, as will appear in the course of thefollowing detailed description of my present preferred Reference is had to the .Figure .1 isra plan view, with parts broken; away, of the top of a sound recording and reproducing machine having applied thereto a tape magazine, the upper half of the latter being'removed; U

Figure 2 is a section on line 2--2 of Figure '1; Figure 3 is a detail perspective of one end portion of a tape guide; J

Figure 4 is a view similar to Figure 3 but showing one part of the tape guide assembly only;

Figure 5 is a transverse section on line 5-.5 of Figure 3; Figure 5a is a section on line. Set-5a of Figure 3; v a

Figure 6 is a section on line 66 of Figure-'1; Figure '7 is a section on line 1-4 of Figure 1; Figure 8 is a section on line 8-8 of Figure 7.; Figure 9 is a section on line 9-9 of Figure 1-; Figure 10 is a section on line l0--l 0 of Figurez; Figure 11 is an enlarged detail of a portion of Figured;

Figure 12 is a fragmentary view of a corner. portion of the lower wall of a magazine showing a modification; v. Figure 12a is a detail section on line l2a-l 2a of Figure 12; and

Figure 13 is adiagrammatic view showlng'z'a preferred embodiment of the electrical circuit .of the invention.

The invention is shown in an exemplary. form applied to a known type of sound recordingand reproducing machine having a main frame understood to mount the main drive motor, drive shafts for two tape reels and two tape driving rollers, and the usual translatingv and erasing magnets, together with a removable tape magazine. For an earlier, disclosure of such a machine, see my application Serial No. 608,734 filed 'August 3, 1945 entitled Tape Drive Sound Recording and .Reproducing Machine; also see Patent Number 2,364,556 to Somers.

Referring now to Figures land 2 of the. drawings, numeral l0 designates generallythe top plate of the main frame of sucha sound. recording and reproducing machine, said plate providing bearings for two reel shafts H and twodrive roller shafts 12 (see also Figure 9), all of which shafts project upwardly a short distance above the surface of the said main frame top'plate, Ill. The two shafts l I will be understood to be driven, as usual, through conventional over-runningor one-way clutches incorporating frictional slip devices as discussed in my aforesaid application Serial No. 608,734, devices of this characterbeing described in more detail in United States Patent Number 2,209,582 to Ross. This part of themachine forms no part of the present invention, and reference to said prior application and patent will sufiice for present purposes. It may however be explained that each one-way clutch drives on the driven take-up reel becomes so great in circumference that the reel tends to wind up the tape at a faster rate than the tape arrives from the positively driven drive rolls. latter, presently to be mentioned in more pare.

ticular, are driven from the shafts .IZ, as [already mentioned.

The magazine includes a base or bottom half consisting of bottom plate 16' having --up-- 1.1

turned marginal flange l1, and also acover or tophalf consisting of a top plate 18 having downturned marginal flange l9 adapted to -fit inside bottom half flange H, as clearly shown in Figby fourxieorner. supponts-wzmeeachconsisting of a spacenizl mounted. oniand fastened to top plate -I inland a. curved positioning flange :22 formed to .receive and position the 'a'rcuate icorner POT, tion :aof-ithe magazine. 'Ihe magazine :will be seenito be ireceivedsnugly inside the founpositioningefianges122,:and ito :rest vdown on the spacers 2|, leaving a predetermined spac'ing'ldistance between the bottomel 6 of the magazine and the top plate I!) of the main frame. The bottom wall 315 iof :the'magazine ha .:a key hole :slot 25 adaptedto receivea bolt 26, which is movably mounted on the main frame plate wand operzable .ot'lock themagazine securely to the latter. Foraamore complete disclosure of this' feature, sseercopending. application Serial No. 720217, filed January 4, 1947 entitled Removable Magazine for Tape, filed by1I-Ierman1S.;I-Ieller and Donald E.

53653; V I v Tightly mounted on each reel shaft H, immediately --above:plate l 0, :is a clutch :collar having vertically projecting drive pin -3l receivable inisocketi32 in ree1hub 33. As'indicated-inFig- 'illrel'. 2,'l':shaf t Ll l projects upwardly through the hub of the tape reel, designated-generally "by :numeralizfid, :and it will be understood that the rreelzisi'freelyiseparable from the shaft I I to per- ..mit'iseparation :of sthe magazine from the maechine. :For details of a preferred construction jjtolthis end, see the -:aforementioned application "Serial:No. 720,2l7. 1 v

IThe- 'bottom :plate i it :of the reel is formed around clutch 230 with :an inward oif-set -35 =adapted to receivethe hub 33 :of the-reel and xlimit its'.downward atravel when the magazine is separated" from the plate l0,-and hence from the clutch 30. Mounted for vertical movement in a circularisaperture. 40 iniaibracket H secured to {the :underside of the magazine cover is a thin metal cup 42 having :a lower central projection 43 .which'is-engageabh'a with the-center of the upl er'end'of the reel shaft when the magazine is on the plate I 0,:and a 'coilspring 44 positioned uins'ide said cup and enga'geable against the upper magazine wall urges saidcupdownw-ardly at all times. Itwillbe evident that whenthemaga- 'zine separated from the machine, this spring- -pres'sed cup will -engagethe reel and will hold it -againstr-the'ofi set -36 while the magazine reels Lare separated' from the machine. thus preventedfrom moving about-and becoming displaced-- within the magazine. 'cup in'p'osition or in. assembly with reference to --bracket "4| when'noireelis present in themaga- =szine, or when'themagazine-cover-is removed, the

The reel is To retain the The .Sumcient depression of the cup against the .spring li-willhowever cause the ears 44a to clear the lugs- 46, so that the cup can be readily assembled or disassembled.

Themagazine will be seen to have a re-entrant notch in its rearward edge, and this notch is adapted to receive the two spaced blocks 5i and 'SZcarrying the erasing and translating electromagnets, the members lil and 52 being understood to be mounted on the aforementioned top frame plate 10. The tworeelstdwill' beQseen tobe positioned near the forward edge of .the magazine, and wound on the hubs .33 thereof .is themagnetic tape 55. The tape. drive ,roliers .56 mounted on the aforementioned shafts 12 are disposed near the rearward edge of-the magazine, on Opposite sides of vthe:not chbll in.such positions that; the tape passing-tangentially between their rearward .sides will extend-across the notch 5i! ,throughthe narrowispaceihetween the twomagnet blocks 5| 7and 52. "Between each roller 55 and the corresponding eel irmthe tape is looped around a frictional guideblocki'l, designed to provide a certain- I'rictional ,restraint on the tape to preventerratic travehof the latter. This block may -be;, gro.ov edandffaced -with. a suitable frictional .material as more particularly described in the aforementioned application LSerial No. 720,217.

- Each tape drive roller iifi. remov bly mounted on the upper end portion of shaft .vl.2,.,andl is clutched thereto amanner similar to the mounting of the reels on the 'reel shafts l,l..

Thus, each roller shaft l2 carries clutch [collar 58 hearing drive-pin 5 9 .engageableina'. socket. .60 in the hub ofroller-SB. =-Whenthe:magazine.is

separated from the machine-roller fifiengag'es the inwardly oif-set wall portion 61 ,of, the-magazinc, and the roller-is engaged, from the -top by spring-pressed cup :63 ofv the =same ptypeflas described in connection-with the reels.

The tape is positively guided across the notch 50, between the two magnet-blocks 5| and- 52,.by a pair ,of guide-members 10 and ll, between which-is formed a closelyfitting .guide-Way l2 for the tape 155. The two projecting end portiqns 73 and 14 'ofthese'members; lflzandili respectively, are formedwithgapeittures 15 in whichgare mounted felt pads (fix-pressed againsti opposite tromagnets with OIJpOSilZGffECGS-Df the tape, as

more particularly explained in the: aforesaid-application Serial No. 720,217: Thefd'etails ofithe translating electromagnets mounted :within the magnet blocks 1 5| -and 52 need-not *be -:given, :as they may be entirely conventional, ormay'beas particularly shown-in an application bfHerman 5; S. Heller and DonaldERoss, filed April 26, 1947, Serial No. 744,190 for'Magnetic Translator ,Coil Assembly For present. purposes, the drawings indicate a-pair of centrally positioned recording.

and reproducing electromagnets 85, and a pair of erasing electromagnets 86 positioned on each side of the magnets 85. e. 7

Referring now to Figure 1'3, each such pair of.

electromagnets will be seen to be electrically,

arm 81 in the listen" position, and also to a. switch contact 90. Microphone 9| is connected by lead 92 to the switch contact 93 opposed to said contact 90, and a switch arm 94 associated therewith is connected by lead 95 to the input side of. amplifier 91. The output side of amplifier SI'Iv is connected by circuit lead 98 to switch contact 99, and a branch lead I from lead 98 connects to switch arm IOI which is adapted to make, contact, in the listen" position of the switch, with contact I02 connected :by lead I03.

to speaker I04.

The two pairs of erasing magnets 86 areconnected by leads H0. to the two-contacts of. a double-throw switch II I, the movable switch arm H2 or which is connected by lead H3-to high frequency oscillator H4 from a source erasing current. A lead H5 containing a suitable voltage dropping resistor H6 connects oscillator I I4 to amplifier output lead 98, for the purpose of supplying a high frequency biasing voltage to the recording electromagnets to aid in the recording function. as well known in the art.

A microswitch I20 having two spring switch arms I2I and I22 adapted normally to make contact with contacts I23 and I24, respectively, is placed in the circuit leads 86 and H3, respectively. For the normal operation of the recording and reproducing machine, these'switch arms HI and I22 are closed with their respective switch contacts. However, they may be opened and held open by the mounting of the magazine on the recording machine for the purpose of decommissioning the erasing and recording functions of the system. Thus, as diagrammatically represented in Figure 13, the lower wall I8 of the magazine has engaged insulation post I30 and spacer I3I to open the two switch arms I2I and I22, and thus open circuit the two leads 88 and H3.

The operation of the circuit of Figure 13 will first be described with the switch arms I2I and I22 of microswitch I20 assumed to be closed. Assuming the direction of the tape 55 to be from left to right in the figure, switch arm H2 would be closed with the contact placing the lefthand erasing coils 86 in circuit. It will beseen that the lefthand erasing coils receive erasing current from oscillator H4 via circuit lead I'l3,'

switch arm H2 and lead H0. Any recording previously on the record tape is thus erased as the tape passes the lefthand pair of erasing magnets, and is in clean condition as it reaches and passes the translating magnets 85. Assuming a recording is to be made, the various switch arms 81, 94 and IOI of switch 88 are thrown to the right, so that microphone 9| is connected through contact 93, switch arm 94, circuit lead 95, amplifier 91, lead 98, contact 99, switch arm 81 and lead 86 to the magnets 85, the switcharm I2I of microswitch I20 being recalled ;as closed under the assumed conditions of operation. At this same time, oscillator H4 supplies a high frequency bias to the recording magnets Viacircuit lead H5 to the amplifier output lead andthenceto the recording magnets by the same, circuit: as just above traced.

For reproduction purposes, and assuming the tape to be, driven in the same direction as bev fore, the erasing magnet switch H2 is thrown to open position (central dotted line position), and switch 88 is thrown to the left. The circuitv is then traced from magnets 85, then acting'as :reproducing magnets, via circuit lead-88a to switch contact 90, thence via switch-arm 94 and lead 95 to the input side of amplifier 91, and

from the output side of the latter vialeads 98 and I00 to. switch arm IOI and finally via contact- I02 and lead I03 to speaker I04. v

Assume now that the placement of the maga-- zine on the machine has operated through-the engagement of its bottom wall I6 with elements I30 and I3i to open the two switch arms of microswitch I20. Lead I I3 is now broken, and it is therefore impossible to convey erasing current from oscillator H4 to erasing magnets 96. Also, it is impossible to make a recordingon the tape reproducing function of the system, since the clr=t cult leads broken by the microswitch I20 play no part during reproduction. Y Referring now to Figures 1 and 6, and illustrative positioning of the microswitch I20xand suitable actuating means therefor is shown. Themicroswitch I20 is shown as mounted onan angle bracket I50 secured to the underside of frame plate I0 directly beneath one of the magazine A plunger I5I is mounted in adrill supports 20. hole I52 extending downwardly through spacer =2I, plate I0 and the wall portion I53 of angle bracket I50 that abuts and is secured to the plate.

I0. The bottom end of this plunger I5I engagesand is normally supported by a'leaf spring I54-secured to bracket I50, but which is adapted, in' turn, when forced downwardly by pressure on said plunger, to engage and depress the movable actuating element I30 of microswitch I20. ."In-

a normal position of the apparatus, the spring I54 holds the plunger I5I in a position with its.

. upper end somewhat raised above the spacer element- 2|, the spring I54 at such timebeing fiat against the underside of wall I53, and the microswitch actuating element I30 being in its upper-i.

most position. Thus, the leaf spring I54 rather than the microswitch is relied upon normally to carry the weight of the plunger I5I. The lower wall of the magazine preferably is provided with a removable element I60, presently described in more particular, adapted to engage the upper end of the plunger I5I when the magazine is] mounted on the machine, and to depress the plunger to the position of Figure 6, whereby to deflect spring I54 in a downward direction and actuate the microswitch I20 by downward en gagement against microswith operating means I30. Thus, the action of mounting the maga- Q zine on the top plate I0 of the machine automatically opens the two circuits controlledbyl the microswitch I20. As already explained, this operation of the microswitch prevents operation of the erasing magnets, and also prevents the translating:magnetslilii fromanakingsazreording I onithe tape: I 7' '3 It will thHSi'bel evident that ifa m'agaziiiewcom' taining a tape bearing a magnetic:recording is proper operation 1 of the machine" is completely guardediagainst" insofar as such operationlmight destroy "the recording onvthe' tape; Complete protection is I afforded iagainstf'the loss of" a vain-'- able zreco'rdingi I On-the other: hand, 'if it' 'isi deisired to employ the'erasing 'and/ or recording fea turesof the- 'machine, the? element IE is removed fromithe' magazine prior tomountingithei magazine": on" the rmachinel In: the preferred illustrative embodiment;..this:removablexelement i6 0. consists simply-of a" known :typeof 1 fastener button'I'wihaving: curved prongs IH which are inserted and engaged aroundthe edge of an aperture. I12 formed in the lower magazine wall.

Preferably; themetal of .thewall I6 around this aperture I12. is dimpledr as 1 at I13, so' that the head of the: button: I m is: flush with the: :lower surface; of the magazine.

tui'e I12; however; thatwitis :not likely tobe'come accidentally dislodged.

-. Removal ofxthe-tbutton' l 10, of: course; permits flier-plunger I! toamove upwardly a short distance;r'theiupper end portion ofrthe-lplunger. be. ing thrust through thesapertu-re' I72, and the spring I54 moving .up againsttheundersi'de: of the; bracketiwall-rl 53v to :Jhold the plunger 'in its elevated position 'Ihe'microswitch I20 is'thus permitted to ."open, the two circuit leads" 86" and I I i 3 automatically: close, and the machines is in conditionto carry out itscomplete erasing and recording functions; as well astthose of reproduction.

Figure: 12' shows ."a' modification; in which "the removablebutton I of theembodimentjust described is replaced by 'a deeply scored circular buttonarea I'IUa of thebottomplate i6 of the magazine; this area being also preferably dim pled; as indicated. It is to'be understood that the scoringline I'I'iib defining this button IIfla isudeep' enough that" the disc area I'Ifla can be easily; knocked out by hitting it. a light blows'withai'punch orother suitable'tool. It is not, however, so weakly'retained in position that it' -will n'ot function to depressthe='microswitch control plunger I5I when left in place.

Once -thi s: knock-out disc has been removed, the j magazinecan again be-reconverted to actuate the switch I20 by inserting-in the aperture left by the removed disc a'button element I'I'U of the type used inthefirst described embodiment. For still other purposes, the magazine need not be providedwith a'removable plunger control ele=- m'en't, but'the unbroken wall I6 maybe relied upon for 1 this-purpose; This latter situation wouldfapply in any-casein'which the magazine was designed to contain a permanent recording)" which-was'in no event to be erased or modified.

Insuch casegit would be unnecessary and even undesirable to" provide for removabilityof the area of the bottom wall I6 above themicroswitch contlrol plunger I51," and hence no provision therefor would'be made; It will beiun'necessaryf' to--rurther illustrate this" final version" or the"- Accordingly, it is impossiblezto either Such a: button I'lll is readily inserted or removed. It has'a sufficiently" tighttengagementl with the edges of the aper-' 1 3 I li e iest I :having its 1 free. end bearing on the; rolL' of tapei'onuone ofthe reels is spivotally'mountedzion astudI'I'BI mountedrin alplate I 60,. fastened to the! bottom wall of. "the magazine, and the'-hub' of this arm "carries; a l gear-sector Is2uin I mesh with: a spur' gear? 1835011: ai sleeve I84'aj ournalled on. stud; I85"mou'nted.-in saidlplatei liarufrhe. upper end of'isleeve" I84.ca'rries an indicator dial I 86,..inscribed. with: :a :suitable scale I 81, which: is visiblerthrough a" small-window I88 in the top' wall of: the magazine. The arm: Iiflflilisx caused normally to bear on the; roll? of tape by" meansi of a coil: spring -89 surrounding-stud: I 81 and connected" between. the magazine. .wail; andfthe. gear sector- 582. It will be clean that. theiarml I80 will swinginwardly and outwardly in accordance with the amount of tape on the corresponding reel 34,18,111 that this movement;

will be indicated byltthe position ofhrlialzrliifi. and itsrscale I81'with;reference'-to thewindow: I88 in the top of the magazine. I. g l I.

The invention has .now been i disclosed by way of aidetaileddescription of certain :presentiill us-strative': embodiments! thereof; 1 These are ton be" understood; ofi-course; as merely: illustrative: rather: than: restrictive on the broad': invention, since various: changesla in /design, structure an'd arrangement may; be: made; without-departing. fromxthezscope: and spiritrof thei-inventiongr Ivclaim: v c 1. In amagnetic-sound recording and: re;-

producing machine vhaving: La; quick. detachable record amagazine ,rreceivable in; an operative positionithereon ther combination of erasing and; reproducing electiomagnets '-.adapted;for :coactiorr with avmag-netic: sound record carriedby zsaid: magazine; v electric circuits for said gelectromagnets, a'decommissioning switch. means 'on{ said:

machine forthe circuit oftsaiderasing elcctro-g magnets. and ea "readily; di'splac'eable, switchv actuating; element onsai-d magaaine. adapted when undisplaced. to engage and actuatesaid.

switch means as the; magazine is mountedin operative position on said machinensaid displaceablel element when displaced avoiding operative engagement withsaidswitch means,- I Y =2. The combination aszplefined in claim -1, wherein said displaceable switch; actuating: element is detachably connected to said magazine. 3. In a magnetic-sound recording. and reproducing machine erasing and v reproducing electromagnets cooperablewith a magnetic sound;

record, electric circuits forsaid nelec tromag nets,

v eansn wn i 11w-.m lm i av magniii sound record on,said ;rnachine for decommissioning saider'asing electrom agnets, said means being readily displaceable torestore the function of said erasing electromagn'ets.

Res-me rs CITED file of this patent: 1

UNITED STATES PATENTS Number 1 Name Dat 2,082,303. Schiller r June. 31;.193'7 

